In the manufacture of metalarc lamps, it is necessary to properly orient and strap mount frames about a glass stem of the lamp. This banding procedure places a metal strap over the mount frames and the glass stem, thus holding the mount frames, with proper orientation, about the glass stem.
The original fabrication procedure hand-crimped the metal strap, resulting in a labor-intensive method. The strap was clinched at a single point about the glass stem and mount frames. In addition to being labor-intensive, this method was ineffective; the proper alignment of the frames about the glass stem was not always achieved. Another problem common to this earlier procedure was maintaining a small, compact configuration of the band around the glass stem, so that subsequent manufacturing processes could be accommodated. A further problem with the aforesaid procedure was its inability to maintain proper stem tolerances and hand crimping pressure. Stem breakage was a fairly common occurrence. Needless to say, the hand clinching of the strap about the lamp frames and glass stem was both costly and inefficient.
The present inventors have developed a new banding procedure that can be used for automatically crimping a new metalarc lamp mount assembly. The metal straps holding the mount frames about the glass stem comprises two banding pieces. The straps provide for proper alignment and radial orientation of the frames. The proper alignment results in part from a pair of pressure-relieving interlocks that are each clinched at opposite pole centers of the strap. The interlocks each comprise a fold-over configuration. Each interlocking portion of the strap allows for material to be pulled back from the fold-over configuration as it is being crimped. The pull-back of the material releases tension along the strap during crimping. The variability in glass stem diameters among lamp units is no longer a factor in banding strap tension. Thus, stem breakage is now substantially eliminated.
The crimps that are formed are very compact. The interlocking portions are physically as close as possible to the glass stem. This compactness resolves the inability of the prior hand procedure to control the final sub-assembly envelope diameter. In other words, the present inventive banding straps provide a more compact and uniform product.